A number of processes for producing a lining on the inner walls of a metallurgical vessel are known. Thus, for example, there is known, according to the prior art, a process in which an aqueous and pasty mixture capable of setting, containing inorganic particles, optionally fibers, and an organic and/or inorganic binder, is applied by molding, tamping or projecting with a trowel, pneumatic tube or other projecting device to the inside of a metallurgical vessel such as a casting tundish. The mixture of particles sinters in contact with the liquid metal, and this ensures the cohesion of the lining.
According to the prior art, there is also known a process according to which at least two layers of different compositions are applied to the inside of the metallurgical vessel, each being applied by projecting an aqueous and pasty mixture capable of setting of the above-mentioned type.
The fluidity of such aqueous and pasty mixtures, which expedites their application, is proportional to the amount of wetting water present. The wetting water employed for forming the aqueous mixture(s) must be removed by drying, and this involves an immobilization time and an expenditure of energy, neither of which can be ignored.
There is also known a process according to which a template is placed inside a metallurgical vessel, a material consisting of refractory particles and of a heat-curable binder is projected pneumatically between the template and the inner walls of the vessel, and heating is then applied while the template is left in place to cause the binder to set, and the template is finally removed. The cast material contains an inorganic compound containing water of crystallization. Water of crystallization is water in chemical combination with a crystal, necessary for the maintenance of crystalline properties but capable of being removed by sufficient heat.
It is also known that refractory bodies can be made by casting of refractory concretes either by vibration casting of a wet concrete or by vibration-free casting of a concrete having a self-flowing consistency. In both approaches, all concrete materials need to be homogeneously mixed and wetted. Customarily, matrix and coarse materials are batched together. Then water is added to give fluidity and to initiate a reaction that forms an end product of an ideal shape. To accomplish this, a large portion of the material is fine-grained matrix material. This material has a high surface area, which lends itself to attack in adverse conditions, such as most refractory applications. Larger proportions of water improve the fluidity of the mixture, but promote the formation of pores in the formed product. A high mixing water content in the castable means very long dry-out times and poor mechanical strength. Smaller proportions of water inhibit pore formation, but yield product pieces that are prone to cracking, crumbling and spalling. In extreme cases, formulations using small proportions of water are unable to form a coherent piece.
In order to increase thermal shock resistance, fibrous materials have been used in vibration-cast materials and in self-flowing materials. The use of fibrous materials increases the need for high levels of mixing water and makes casting more difficult. Very coarse materials which are beneficial for slag resistance due to their high density can only be used to a certain extent, because casting of concretes with a very high content of coarse materials is very difficult.
Infiltration processes are also used to produce objects containing coarse particulates intermingled with finer particulates introduced in the form of a slurry. For example, a mold may be filled with dry coarse particulates which can have a size between about 1 and 60 mm to form a formed dry body. The formed dry body is then infiltrated with a slurry consisting of a binder, water, and fine filler materials having a particle size distribution of between 0.0001 to 3 mm. Infiltration according to this method is a time-consuming process. The difficulty of production of a thick piece by this method increases with the piece's thickness, unless a larger aggregate is used.
The aim of the present invention is to overcome the disadvantages of the known compositions and to produce a product in which the amount of mixing water is minimized, the quantities of matrix material are minimized, the porosity of the formed dry body is minimized, the density of the formed dry body is increased, and a product having enhanced modulus of rupture and cold crushing strength values is produced.